need advice asap !!!

so i’ve been dating my boyfriend for a few months now and he’s had sex with a few people and tried some things before we dated but i on the other hand was a virgin when we started dating and lost my virginity to him. i’m usually willing to try new stuff with him and about a month and a half ago he wanted to try anal. i agreed and it hurt really bad at first but he kept going and eventually it felt good but then i was really sore for a few days after and so now whenever he asks i keep saying no and idk why but it just makes him so upset and it always starts arguments and fights between us. he has a lot going on rn so that might be a bigger part of it but idk why doing anal is such a big deal for him and the only reason he will give me is that he likes it. i tried one more time recently but i had to ask him to stop because it hurt so bad. i’m just tired of arguing over this and idk why he gets so upset so if anyone has any ideas why it’s such a big deal or even has tips on how to make it easier on my end so i can try it again because after the initial pain it was good i just need help on how to get through that initial pain. please help !!